The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without payment of any royalties thereon or therefor.
Not applicable.
1. Field of the Invention
The present application is related to a system and method of launching small devices from a submarine and, in particular, to a system and method of launching small devices from a submarine with a minimal acoustic signature.
2. Description of the Prior Art
Generally, small device launch systems generate what is known as a xe2x80x9cwater hammer,xe2x80x9d which is a waterborne acoustic signal. One example of such a small device launching system is illustrated herein with references to FIGS. 1 and 2. This system includes a tank 10 with an internal piston chamber 12 defined by a chamber wall indicated generally at 14, which is generally cylindrical and includes opposing chamber end wall 16 and stroke wall 18, which conform to the shape of chamber wall 14. A plurality of bumpers 20 are generally disposed within piston chamber 12 on the opposing walls 16 and 18.
At end wall 16, piston chamber 12 is fluidly connected to a high pressure air source (not illustrated) by a passageway 24. At stroke wall 18, piston chamber 12 is fluidly connected to a conventional launch tube (not illustrated) by a launcher bore 26 having generally cylindrical sidewall 28 along which a plurality of deceleration discs 30 are disposed.
A piston indicated generally at 32 is slidably disposed within piston chamber 12. Piston 32 has a cross-sectional shape generally conforming to chamber wall 14, and is supported on a piston shaft 34. Piston 32 and piston shaft 34 are co-axially disposed within piston chamber 12. Piston 32 includes opposing surfaces 36, 38 which will be referenced hereinafter as air side surface 36 and water side surface 38. Water side surface 38 of piston 32 includes a cylindrical extension 40 having a conical end 42.
In operation, when it is desired to launch a device from a launch tube (not illustrated), high pressure air from the high pressure air source is delivered to piston chamber 12 through passageway 24. The air is delivered at a pressure greater than sea pressure at the depth of the submarine. Thus, as shown in FIG. 2, piston 32 is forced toward stroke wall 18, compressing water adjacent water side surface 38 of piston 32 through launcher bore 26 and into the breech end of a launch tube connected to the system. The movement of the water creates a pressure imbalance between the breech end of a device in the launch tube and, as a result of the pressure imbalance, the device is ejected from the launch tube.
Of course, as the depth of the submarine increases, so does the sea pressure, which increases the pressure on the muzzle end of the launch tube. As a result, the pressure requirement for satisfactorily effecting the launch of a device from the launch tube increases with the depth of the submarine. In addition, when piston 32 impacts stroke wall 18, the system hardware is shock loaded and a high level airborne and waterborne acoustic signature is generated, as described above.
In order to minimize such undesirable effects, rubber bumpers 20, as described above, are generally incorporated into both end walls 16, 18 of piston chamber 12.
In addition, deceleration discs 30 work in conjunction with conical end 42 of extension 40 to restrict the flow of water from water side surface 38 of piston 32, to the launch tube, at the end of the stroke. As piston 32 moves toward stroke wall 18, an increasing number of deceleration disks 30 are effectively sealed against fluid flow by extension 40. As a result, the pressure increases on water side surface 38 of piston 32. The increasing pressure counteracts the high air pressure on air side surface 36 of piston 32, in an attempt to decelerate the rate at which the piston 32 travels and hits stroke wall 18.
Despite the deceleration effected by the bumpers 20 and the deceleration disks 30, a column of water in launcher bore 26 leading to the launch tube continues to flow in the direction of the launch tube. The momentum of the column of water creates a low pressure region proximate the tank in the region of the launch tube in closest proximity to launcher bore 26. The low pressure region results in an abrupt stop of water flow in launcher bore 26, which creates cavitation or a water hammer.
Various fluid filled piston assemblies are provided in the prior art. These include:
U.S. Pat. No. 5,004,264 to Kozaki et al. discloses a piston control device in which a fluid-operated valve controls the position of a piston in a fluid-filled cylinder.
U.S. Pat. No. 5,107,969 to Klein et al. discloses a controllable vibration damper having a fluid filled cylinder with a piston disposed therein. A control valve is provided in the piston for regulating fluid flow across the piston interface.
U.S. Pat. No. 5,174,236 to Moody discloses a torpedo launch system using synthetic cushions as piston brakes.
U.S. Pat. No. 5,337,864 to Sjostrom discloses a suspension system used as a fluid-filled piston assembly in which upper and lower chambers thereof are coupled to one another via a throttle valve.
U.S. Pat. No. 5,392,882 to Mackovjak et al. discloses a suspension strut in which a spring-loaded mass divides a fluid-filled cylinder into two chambers that are coupled to one another by a valve.
U.S. Pat. No. 5,810,125 to Gezari discloses an active shock absorber seating system which can decelerate a piston based on the position of the piston""s hydraulic cylinder.
None of these devices provides a means for controlling water hammer in a small device launcher.
It is a first object of this invention to provide a small device launcher incorporating a means for avoiding water hammer.
It is another object of this invention that such launcher be configurable to different launch profiles.
It is yet another object of this invention that such added capabilities be provided with minimal modification of existing small device launchers.
Accordingly, this invention provides a system for launching a small device from a submarine, including a chamber fluidly connected to a high pressure air source and to a launcher bore, a first piston disposed within the chamber, the piston being connected to a piston shaft. A piston shaft extension is connected to the piston shaft and extends through an aperture in the housing. A hydraulic control cylinder is operatively connected to the piston shaft extension. A controller is included for controlling the relative movement of the hydraulic control cylinder. The hydraulic control cylinder is responsive to the controller and controls the relative position of the piston shaft extension.
Another embodiment is directed to a small device launching system. The system includes a housing having an air source port and a launcher-bore, and a piston shaft aperture disposed coaxially within the housing. The system also includes a piston slidably disposed in the housing between the air source port and the launcher bore. A piston shaft is joined to the piston, and at least a portion of the piston shaft extends outside of the housing through the piston shaft aperture. A hydraulic braking assembly is joined to the portion of the piston shaft extending outside of the housing. A position indicator is joined to the piston shaft and provides a signal responsive to the position of the piston. The controller is joined to receive the signal from the position indicator. The controller is joined to control the hydraulic braking assembly.